A missing .env file no longer causes a fatal error. Env vars can now
come from the container environment (Docker/systemd) or a .env file
interchangeably.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
Avoids collision with standard Linux shell variables that would cause
silent authentication failures against the IMAP server.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>